GB838809A - Improvements in or relating to magnetic switching circuits - Google Patents

Abstract

838,809. Magnetic gating circuits. STANDARD TELEPHONES & CABLES Ltd. Oct. 17, 1958, No. 33208/58. Class 40 (9). A gating circuit which will produce an output indicating the presence of a number of input signals comprises x input windings each wound on a different combination of z cores, x output windings each wound on a different combination of cores, and each core having unique combinations of y input and y output windings. The number of cores equals the number of choices of y out of x. As shown in Fig. 3, three input signals at terminals 31, 32 and 33 hold cores 21, 22 and 23 saturated. Withdrawal of one signal does not affect the saturation of the cores as each core is saturated from two of the signal sources. Withdrawal of two signals will desaturate one core and as this is associated with two output windings two of the terminals 41, 42 and 43 will show a high impedance. Withdrawal of all signals will desaturate all cores and all output circuits will show a high impedance. Input and output circuits are shown in Fig. 4, the input windings being energized over normallymade contacts S1, S2 and S3, and the output windings being energized in parallel from an A.C. source. Transformers T1, T2, T3, normally extract sufficient voltage to break down the voltage thresholds of rectifier bridges MR1, MR2, MR3. When two or three contacts S1, S2, S3 are open two or three of the output circuits show high impedance and the associated rectifier bridges cut off, causing indicators I1, I2, I3 to operate. The transformers T1, T2, T3 may be connected in common in a series connection of a number of output circuits each in a separate gating circuit, such as shown in Fig. 3, with separate sets of contacts S1, S2, and S3, see Fig. 6, not shown. In this arrangement the indicators I1, I2 and I3 will show that one of the gating circuits has two or three contacts open but will not show which gating circuit is concerned.